拟南芥MAPK3/6-MKT1在真菌毒素草酸诱导的植物细胞程序化死亡中的功能

Programmed cell death (PCD) in plants plays important roles in plant development and responses to both biotic and abiotic stresses. But the induction of PCD in plants can be either beneficial or harmful to plants themselves. Plant diseases can cause significant reduction in crop yield. A necrotrophic fungus, Sclerotinia sclerotiorum, can colonize over 400 host plant species. The diseases caused by S. sclerotiorum are very difficult to control by either genetic or chemical strategy. It has been found that axalic acid (OA) is a pivotal pathogenicity determinant of this fungus, it contributes to the pathogenic success by inducing PCD in plant that is indispensable for disease development. However, the underlying mechanism and signaling pathway of plant PCD induced by OA remain largely unknown. . Based on our preliminary data, we found that OA can activate MAPK3/6. Furthermore, a transcription factor, MKT1, serves as a substrate of MAPK3, which phosphorylates MKT1 in vitro. In addition, MKT1 is able to bind to the W-boxes in the promoter of WRKY46, a marker gene of plant HR related PCD. Moreover, the binding of MKT1 to WRKY46 promoter is repressed by MAPK3. To investigate the exact role of MAPK3-MKT1-WRKY46 in the signaling of plant PCD induced by OA, we are planning to perform the following experiments using multiple approaches: the PCD related phenotype analysis of both MKT1 gene over-expression transgenic plants and MKT1-derived T-DNA mutants; the PCD related phenotype analysis of mapk3 and mapk6 mutants; examining the function of MKT1 phosphorylation by MAPK3; the confirmation of interaction between MAPK3 and MKT1 both in vitro and in vivo. Our work will help to understand the underlying mechanism of palnt PCD indcuced by OA during S. sclerotiorum infection.

植物细胞程序化死亡是一种重要的生命现象。病害是影响农作物产量的主要因素之一。核盘菌是一种是危害作物和蔬菜的世界性病原真菌，它通过分泌真菌毒素草酸来诱导宿主发生细胞程序化死亡，从而实现侵染。但人们对这一过程背后的分子机理却知之甚少。在前期工作中，我们发现草酸可以激活拟南芥MAPK3/6。我们筛选到一个MAPK3的底物：转录因子MKT1。MKT1可以和植物细胞程序化死亡标志基因WRKY46的启动子相结合，而MAPK3却抑制了这一结合。. 本项目将通过遗传、生化等多种手段，对MAPK3/6和 MKT1在草酸诱导的植物细胞程序化死亡中的功能进行深入研究。鉴定MAPK3磷酸化MKT1的位点，分析磷酸化的功能。最终阐明MAPK3-MKT1-WKRY46这一新的信号链条的作用机制。该研究不仅有助于促进对植物细胞程序化死亡的了解，也将为农业上防治核盘菌病害提供理论基础。

病害是影响农作物产量的主要因素之一。一些真菌如核盘菌等，能够通过分泌真菌毒素草酸来诱导宿主发生细胞死亡从而实现侵染。为了解析草酸诱导植物细胞死亡的分子机制，在该项目的支持下，我们开展了拟南芥MAPK3/6-MKT1在草酸诱导植物细死亡中的功能研究。.我们发现草酸可以诱导拟南芥MAPK3/6的激活。与天然植物免疫过程中的MAPK3/6激活不同，草酸诱导的MAPK3/6激活不依赖于免疫受体复合物中的FLS2、BAK1和BIK1等组分。而且，草酸诱导的MAPK激活可以持续2个小时之久。另外，MAPK3可以和转录因子MKT1相互作用，而且，二者的互作发生在细胞核。MAPK3可以磷酸化转录因子MKT1，MAPK3磷酸化MKT1的位点位于MKT1的5个保守的S(T)P基序中。而MKT1可以和植物细胞程序化死亡标志基因WRKY46的启动子相结合，而MAPK3则抑制了MKTI与WRKY46启动子的结合。通过分析mapk3 和mapk6 突变体材料的细胞死亡表型，我们发现MAPK3和MAPK6在草酸诱导的植物细胞死亡中起负调控作用。另外，我们对草酸处理的拟南芥的转录组进行了分析，发现了一些重要的响应草酸处理和参与细胞死亡的基因，为今后研究草酸诱导植物细胞死亡奠定了基础。.总之，我们发现了MAPK3-MKT1-WRKY46这一信号链条调控草酸诱导植物细胞死亡的机制。该研究不仅有助于促进对植物细胞程序化死亡的了解，也为农业上防治核盘菌病害提供了理论基础。

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